major cleanup of tsig datastructures and extend/merge operations; fixes old bugs in classes/arities code; proper treatment of nonterminals and syntax-only types;
use "bool2if.ML";
use "proof.ML";
qed "bool2if_correct";
use "normif.ML";
use "proof.ML";
qed_spec_mp "normif_correct";
Addsimps [normif_correct];
use "norm.ML";
use "proof.ML";
qed "norm_correct";
use "normal_normif.ML";
use "proof.ML";
qed_spec_mp "normal_normif";
Addsimps [normal_normif];
use "normal_norm.ML";
use "proof.ML";
qed "normal_norm";